High-pressure boiler tubes are frequently occurs fault because of high temperatures, affecting the entire heating system, mainly due to an internal boiler for heat treatment is not perfect, a lot of heat can not be effectively converted and timely treatment.
Generally refers to the high-pressure boiler tube heating is too high, causing not only lead to coarse grains, and grain boundary melting or partial oxidation occurs, leading to the weakening of the grain boundary, known as the over-burning. After the serious deterioration of steel over-burning performance, the formation of cracks during quenching. In the event of over-burning phenomenon, the occurrence of structural components can not be burned into them again, only to eliminate, not only is the device to introduce economic waste, but also affect the stability of the entire heating system. For this reason, in the course, we must take preventive measures, preventive measures to reduce the probability of burning had occurred.
Overheating than over-burning phenomenon, its harm is relatively low, there have been burning phenomenon of structural components must be eliminated, and structural components overheating cooling treatment can be achieved by taking measures to continue the operation of components.
Decarbonization and oxidation
Just upon heating, the surface layer of the medium of oxygen and carbon, hydrogen, carbon dioxide and water vapor react, after reducing the surface carbon concentration is called decarburization off steel quench surface hardness, fatigue strength and abrasion resistance is lowered, and surface residual tensile stress is easy to form a mesh surface cracks. Upon heating, the alloying elements iron and steel surfaces and medium oxygen, carbon dioxide, water vapor and other phenomena occurring oxide film produced by the reaction is called oxidation. After the high temperature oxidation of the workpiece dimensional accuracy and surface brightness deterioration of the oxide film has poor hardenability steel prone to hardening soft spots.
Ductility and toughness decrease when heated at the scene in the hydrogen rich gas called hydrogen embrittlement of high strength steels. Workpiece appear in addition to hydrogen embrittlement by hydrogen embrittlement treatment can eliminate, the use of vacuum or inert gas atmosphere with low hydrogen heating can avoid hydrogen embrittlement.
Post time: Oct-10-2019